Toto UltraMax II Sounds Like It's Leaking Then Makes Strange Noise

I have a Toto Ultra Max II (CST 604CEFG) that is under 2 years old. Recently it has started to make noise as if it's leaking then it will make a loud sound as if it's filling up the toilet. When it first started less than a month ago the loud sound was last a second or two, yesterday it lasted 3 to 5 seconds and happened a few times per hour.

When I would touch the green fill valve and the screw type item on the fill valve, it would duplicate the 'filling up' noise, but I could not get the leak sound to go away or the short fill sound to stop so I cut the water to the toilet for the time being.

It may be water leaking past the flapper and causing the tank to refill.

Make sure the shutoff at the wall is open all the way.

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Now that you have had the water turned off for a while, take a look in the tank. Has the water level dropped? That's a good indication that the flapper needs to be replaced, something that is routine maintenance for a toilet.

An American company named Korky makes many of the internal parts for Toto toilets. Korky is the inventor of the flapper, and is the number one maker of original equipment flappers (i.e. that manufacturers use under their own brand) and replacement flappers that fit specific toilets or brands. Korky makes a flapper for your Ultramax; the easiest way to replace it is to get the model 3060 "universal adiustable" 3-inch one from Korky, which is available at Lowes (who calls it model 3060bp). It is called model 3060cm at Home Depot. It is available at myriad local stores, at Grainger, and online as well. It should sell for between $11 and $15. You have a 3" flush valve on your Ultramax for extra flush power, not a traditional 2", so you need the 3" flapper.

The Toto part number for your flapper is THU331S. If you use that one, you won't need to adjust it, although I kind of like the ability to adjust it. That would be available at a local plumbing supply shop or online, although the latter source is often overpriced. Toto's list price for that flapper is $21, although they are currently out of stock at the Toto web site. Because Korky makes a lot of flappers for Toto, there is no advantage in buying the official Toto part.

Installing a flapper is an easy DIY job, no tools required. Should take less than 5 minutes.

Just picked up the Korky 3" flapper. The Toto Ultra Max II is not listed on the grid of models with a number to select on the flapper.

What number should be selected?

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It's a little late to call Korky to ask them today (I just tried), but the other method is more precise anyway.

Open the lid with the current flapper in place. Flush. Watch where the water level is when the flapper closes. You will notice that the tank doesn't empty -- it's not supposed to. It doesn't use all the water in the tank. instead, it uses the weight of the extra water to push the water that it does use through the flush valve.

Mark that level with a pencil (or eyeball it). Install the new flapper set at, say, 6. Flush. If it closes at the water level that the old one closed, you're done. If not, you can adjust the number as follows: if the thing doesn't close until the water level is lower than it used to be, then it's putting too much water through the valve, and you need to "turn it down" to a lower number. If it closes with the water level higher than it used to be, then it's not putting enough water through the valve, and you need to "turn it up" to a higher number.

Two years is a little short for life unless you put chemicals into the tank. If you do - STOP! Chemicals in the tank will deteriorate the rubber parts fairly quickly. One company does make one that fits in the tank, but fits in-line with the refill hose to run that into the bowl (IOW, it does not put anything into the tank). The II versions of the Totos are 1.28g. I'm not sure Lowes has the proper flapper valve and it may stay open to let 1.6g rather than the 1.28g.

Okay, so I am replacing this last post, because I stand corrected. The "E" series Drake (1.28gpf) uses a different flapper than the "S" series Drake (1.6), which makes sense because both toilets use the same china tank. So you can't use the Korky 2021BP (Red) "Fits Toto" flapper on the E series Drake (and presumably a bunch of the 1.28gpf toilets), at least not if you want it still to be a 1.28gpf toilet.

HOWEVER, it turns out that the current manufacturer's-specified flapper for the 1.6gpf Drake CST744S is model THU331S, which is the very same flapper now being used on the Ultramax II. Presumably both toilets require the flapper to close at the same water depth, although the tank shape is different and less water goes through the valve on the Ultramax II at that water depth. SO, even though the Red "Fits Toto" 2021BP flapper (the equivalent of the Toto THU331S) was originally designed for a GMAX flush, it is a correct replacement flapper on the Ultramax II. It has become a little hard to find since Korky came out with the adjustable 3" flapper; you can carry the correct replacement flapper for all 3" Totos just by carrying that. So, for example, Lowe's shows the 2021PK flapper on it's web site, but it isn't available anywhere in the New York area and isn't available from Lowe's online. Plainly, they are shifting over to carrying just the adjustable one. Same with HD, who actually sells it online-only for a few cents more than the adjustable one, which it sells in stores.

So, for the original poster, you did the right thing by getting the adjustable one, and its setting should probably be "6", the same as the Drake ST743 mentioned in the instructions (which is presumably the 1.6gpf version of that tank). See how that works and let us know.

CLIFF NOTES: The Korky Red "Fits Toto" GMax flapper, 2021BP, is an acceptable replacement flapper, surprisingly-enough, on the 1.28gpf Ultramax II, if you can find it. (It is also acceptable replacement on the toilets listed below.)

The Korky Adjustable 3" flapper, 3060BP, should work well at a setting of "6" on the 1.28gpf Ultramax II. However, verify this by marking the water level where the old flapper closed and see if the new flapper shuts at the same water level when set at "6".

The replacement Korky 2021BP "Fits Toto" Red Flapper, although not at HD or Lowe's, but it's likely cheaper in the end to just get the adjustable one, 3060BP (or PK or CM, at L and HD, respectively) at Lowe's or HD or your local hardware store.

Just installed a Toto Carlyle II and noted it kept sounding like it was running. After cursing my new "high efficiency" toilet, I watched the operation. It is NOT the flapper everyone is talking about. The leak noise still can be heard with the water turned off and below the edge the flapper seats on. Our unit has 2 screws which holds the flapper seat tight against the body. One of the 2 screws has a stripped head and I suspect this is too loose causing a poor seating between the one-piece toilet and the flapper seat. I turned the water off and the leak noise only stops well below the seat level. The flapper may not be the issue. Going back to our local store on Monday for resolution.

replaced the whole seat and flapper assembly. Found when I lifted the 'old' assembly by loosening the 2 screws, there was a piece of white debris stuck in the rubber cup gasket that seals the tank to the flapper assembly. This was causing the water to by-pass and constantly drain the tank. Works like a charm now